A polishing liquid used for chemical mechanical polishing includes colloidal silica, in which a zeta potential of the colloidal silica measured in a state where the colloidal silica is present in the polishing liquid is −20 mV or less, an electrical conductivity is 200 μS/cm or less, a pH is 2 to 6, and a transmittance is 70% to 99%.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A polishing liquid used for chemical mechanical polishing, the polishing liquid comprising: colloidal silica, wherein a zeta potential of the colloidal silica measured in a state where the colloidal silica is present in the polishing liquid is −20 mV or less, an electrical conductivity is 200 μS/cm or less, a pH is 2 to 6, and a transmittance is 70% to 99%.
2. The polishing liquid according to claim 1 , wherein an average aspect ratio of the colloidal silica is 1.5 to 2.0.
3. The polishing liquid according to claim 1 , wherein a diffusion electrical double layer is formed on a surface of the colloidal silica, the diffusion electrical double layer has a fixing layer formed on the surface side of the colloidal silica, and a diffusion layer formed outside the fixing layer, and a thickness of the diffusion layer is 10 to 1,000 Å.
4. The polishing liquid according to claim 1 , wherein, in a case where a pH of the polishing liquid is denoted by X, and a zeta potential of the colloidal silica measured in a state where the colloidal silica is present in the polishing liquid is denoted by Y, a zeta potential in a case where a pH of the polishing liquid is set to X+1, and a zeta potential in a case where a pH of the polishing liquid is set to X−1 are both within a range of Y±5 mV.
5. The polishing liquid according to claim 1 , wherein an average primary particle size of the colloidal silica is 15 nm or less.
6. The polishing liquid according to claim 1 , wherein the electrical conductivity is 0.05 to 200 μS/cm.
7. The polishing liquid according to claim 1 , wherein the colloidal silica has, on a surface thereof, at least one group selected from the group consisting of a sulfonic acid group, a phosphonic acid group, and a carboxylic acid group.
8. The polishing liquid according to claim 1 , further comprising: an acid component, wherein the acid component is at least one compound selected from the group consisting of a compound having an acid group and a basic group, and phosphoric acid.
9. The polishing liquid according to claim 8 , wherein the compound having an acid group and a basic group has a cyclic structure.
10. The polishing liquid according to claim 1 , further comprising a compound having a heterocyclic ring having two or more nitrogen atoms.
11. The polishing liquid according to claim 1 , wherein, in a case where the polishing liquid is used for polishing silicon nitride and silicon oxide, a ratio of a polishing speed for the silicon nitride to a polishing speed for the silicon oxide is 10 or more.
12. The polishing liquid according to claim 1 , further comprising a cationic surfactant or an amphoteric surfactant.
13. The polishing liquid according to claim 12 , wherein, in a case where the polishing liquid is used for polishing silicon nitride and polysilicon, a ratio of a polishing speed for the silicon nitride to a polishing speed for the polysilicon is 0.25 to 4.
14. The polishing liquid according to claim 1 , further comprising an anionic surfactant.
15. The polishing liquid according to claim 14 , wherein, in a case where the polishing liquid is used for polishing silicon nitride and polysilicon, a ratio of a polishing speed for the silicon nitride to a polishing speed for the polysilicon is 4 to 100.
16. A chemical mechanical polishing method comprising: a step of bringing a polishing target surface of a polishing target object into contact with a polishing pad while supplying the polishing liquid according to claim 1 to the polishing pad attached to a polishing platen, relatively moving the polishing target object and the polishing pad to polish the polishing target surface, and obtaining a polished polishing target object.
17. The chemical mechanical polishing method according to claim 16 , wherein the polishing target object contains silicon nitride and silicon oxide.
18. The chemical mechanical polishing method according to claim 17 , wherein the polishing target object further contains polysilicon.
19. The polishing liquid according to claim 1 , further comprising: a compound having an acid group and a basic group.
20. The polishing liquid according to claim 1 , further comprising: phosphoric acid.
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August 4, 2020
March 8, 2022
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